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1.
We reported γ‐alumina supported molybdenum phosphide (MoP) catalysts as a novel catalyst for sulfur‐resistant methanation reaction. The precursors of the catalyst were prepared by impregnation method and the effect of reduction temperatures (550 °C, 600 °C, 650 °C) of the precursors for sulfur‐resistant methanation was examined. The results indicated catalyst obtained by lower reduction temperature delivered better sulfur‐resistant methanation performance. Meanwhile, the influence of H2/CO ratios and H2S content was also investigated. The results indicated that high H2/CO ratio and low H2S content was favorable for methanation of MoP catalysts. The catalysts were characterized by N2 adsorption–desorption, XRD, XPS and TEM. The results confirmed that the MoP phase was formed on all the catalysts and the physicochemical properties of the samples influenced the performance for sulfur‐resistant methanation. 相似文献
2.
In this paper, the effect of additive Fe on Ni/Al2O3 catalyst for CO2 methanation was studied. A series of bimetallic Ni–Fe catalysts with different Ni/Fe ratios were prepared by impregnation method. For comparison, monometallic Fe‐based and Ni‐based catalysts were also prepared by the same method. The characterization results showed that adding Fe to Ni catalyst on the premise of a low Ni loading(≦12 wt.%) enhanced CO2 methanation performance. However, when the Ni loading reached 12 wt.%, the catalytic activity decreased with the increase of Fe content, but still higher than the corresponding Ni‐based catalyst without Fe. Among them, the 12Ni3Fe catalyst exhibited the highest CO2 conversion of 84.3 % and nearly 100% CH4 selectivity at 50000 ml g‐1 h‐1 and 420 °C. The enhancement effect of adding Fe on CO2 methanation was attributed to the dual effect of suitable electronic environment and increased reducibility generated by Fe species. 相似文献
3.
The supported Ni-based catalyst is widely used in the methanation process. Nevertheless, the major disadvantages of this catalyst are a poor behavior in the water-gas-shift (WGS) reaction and the deactivation at higher temperatures. A new kind of catalyst, nickel-containing oxides catalyst (NiMgAl), obtained from thermal treatment of hydrotalcite-like compounds (HTlcs) was prepared using the co-precipitation method. The performance of this catalyst was systematically investigated and compared with that of the Ni/Al2O3 catalyst. It was found that the NiMgAl catalyst shows an enhanced methanation activity compared to that of the Ni/Al2O3 catalyst and the former catalyst shows a better performance for the methanation especially at temperature over 550°C. Three NiMgAl catalysts with different nickel content were prepared and tested in the methanation operated at a GHSV of 15000 h?1 and n(H2)/n(CO) of 1.5. The results indicate that with the NiMg8 catalyst a higher activity and stability could be achieved than with the NiMg5 and NiMg6 samples, the effect mainly attributed to a higher extent of Ni dispersion was confirmed by XRD results. 相似文献
4.
《Journal of Energy Chemistry》2014,23(2):221-226
In this work, a series of coal-based active carbon(CAC) catalysts loaded by Al2O3were prepared by sol-gel method and used for the simultaneous catalytic hydrolysis of carbonyl sulfide(COS) and carbon disulfide(CS2) at relatively low temperatures of 30-70 ℃. The influences of calcinations temperatures and operation conditions such as: reaction temperature, O2concentration, gas hourly space velocity(GHSV) and relative humidity(RH) were also discussed respectively. The results showed that catalysts with 5.0 wt% Al2O3calcined at 300 ℃ had superior activity for the simultaneous catalytic hydrolysis of COS and CS2. When the reaction temperature was above 50 ℃, catalytic hydrolysis activity of COS could be enhanced but that of CS2was inhibited. Too high RH could make the catalytic hydrolysis activities of COS and CS2decrease. A small amount of O2introduction could enhance the simultaneous catalytic hydrolysis activities of COS and CS2. 相似文献
5.
This study investigated the selective catalytic reduction (SCR) of nitrogen oxides (NOx) with hydrocarbon in the presence of excess oxygen using various composition ratios of Pt/Al2O3, Rh/Al2O3 catalyst mixtures. The composition ratios were 1:1, 1:2, 2:1, 1:3 and 3:1 of 1 wt% Pt/Al2O3 and Rh/Al2O3, which are known to exhibit efficient NOx reduction at low and high temperatures among the noble metal catalysts. Experiments conducted on a single reductant revealed that more efficient NOx conversion could be obtained when Pt/Al2O3 and Rh/Al2O3 were mixed at a ratio of 3:1, rather than 1:1 or 1:3. In a single reductant condition, C3H6 800 ppm (2400 ppmC1) and 400 ppm (1200 ppmC1) exhibited 50% and 38% NOx conversion efficiency at 200°C, respectively. However, NOx conversion efficiency gradually decreased when temperatures were increased above 250°C. With regard to Pt/Al2O3 and Rh/Al2O3 ratio, higher ratios of Rh/Al2O3 activated this Pt+Rh/Al2O3 catalyst in the high temperature range. 相似文献
6.
Solid-state reactions in Y2O3:3Al2O3:4B2O3 system studied by FTIR spectroscopy and X-ray diffraction
《Vibrational Spectroscopy》2000,22(1-2):169-173
In the Y2O3:3Al2O3:4B2O3 system infrared absorption spectroscopy and X-ray diffraction have been used to study the solid-state reactions in the 600–1300°C temperature range. The expected YAl3(BO3)4 formation (whose optimum temperature is at about 1150°C) was proceeded and accompanied by the appearance of YBO3 and Al4B2O9 intermediate phases. At higher temperatures the Al18B4O33 phase was also identified with both methods. Based on these results, some chemical reactions were suggested. 相似文献
7.
V. N. Snytnikov V. O. Stoyanovskii T. V. Larina O. P. Krivoruchko V. A. Ushakov V. N. Parmon 《Kinetics and Catalysis》2008,49(2):291-298
The laser-induced luminescence of Cr3+ impurity ions in model Fe/Al2O3 and Cr/Al2O3 catalysts with different calcination temperatures was studied. It was found that an additional luminescence band at 770 nm appeared in the luminescence spectra of low-temperature samples as a result of the interaction of octahedrally coordinated Cr3+ ions with Fe3+ impurity ions. In the θ-Al2O3 phase with a concentration of Cr3+ ions higher than 0.1 wt %, the interaction of the Cr3+-Cr3+ ion pairs in the immediate surroundings resulted in the appearance of N θ lines due to the splitting of R θ lines. The differences of these lines from the N α lines of α-Al2O3 were related to the individuality of the crystal lattice of the θ phase and the coordination of Cr3+ impurity ions in the immediate surroundings, which is different from that in the α phase. Based on the laser-induced luminescence spectroscopic data, it was found that regions with a local Cr3+ concentration higher than the average Cr3+ concentration in the bulk of a catalyst by one order of magnitude were formed in the α-Al2O3-Fe2O3 system with the bulk Fe and Cr concentrations of 2.5 and 0.04 wt %, respectively, which was calcined at 1220°C, as a result of the diffusion of chromium and iron ions. 相似文献
8.
A. V. Pashigreva G. A. Bukhtiyarova O. V. Klimov G. S. Litvak A. S. Noskov 《Kinetics and Catalysis》2008,49(6):812-820
The effect of the heat treatment temperature on the sulfidation and activity of CoMo/Al2O3 catalysts designed for deep hydrodesulfurization of diesel fuel was studied. The catalysts were prepared using citric acid as a chelating ligand. The organic ligands present in the samples heat-treated at 110 and 220°C retard the decomposition of dimethyl disulfide and the formation of the sulfide phase but make the catalyst more active than the samples calcined at higher temperatures. 相似文献
9.
In view of the susceptibility of TiB2 to oxidation, the thermal stability of monolithic TiB2 and of Al2O3-30 vol% TiB2 and Si3N4-20 vol% TiB2 composites was investigated. The temperature at which TiB2 ceramic starts to oxidize is about 400°C, oxidation kinetics being controlled by diffusion up toT≈900°C and in the first stage of the oxidation at 1000°C and 1100°C (up to 800 min and 500 min respectively), and by a linear law at higher temperatures and for longer periods. Weight gains in the Al2O3-TiB2 composite can be detected only at temperatures above ≈700°C and the rate governing step of the oxidation reaction is characterized by a one-dimensional diffusion mechanism atT=700°C andT=800°C and by two-dimensional diffusion at higher temperatures. Concerning the Si3N4-TiB2 composite, three different oxidation behaviours related to the temperature were observed, i.e. up to ≈1000°C the reaction detected regards only the second phase; at ≈1000<T<≈1200°C, the diffusion of O2 or N2 through an oxide layer is proposed as the rate-governing step; atT〉=1200°C, a linear kinetic indicates the formation of a non protective scale. 相似文献
10.
Salmiah Jamal Mat Rosid Susilawati Toemen Wan Azelee Wan Abu Bakar A.H. Zamani Wan Nur Aini Wan Mokhtar 《Journal of Saudi Chemical Society》2019,23(3):284-293
Carbon dioxide emission to the atmosphere is worsened as all the industries emit greenhouse gases (GHGs) to the atmosphere, particularly from refinery industries. The catalytic chemical conversion through methanation reaction is the most promising technology to convert this harmful CO2 gas to wealth CH4 gas for the combustion. Thus, supported neodymium oxide based catalyst doped with manganese and ruthenium was prepared via wet impregnation route. The screening was initiated with a series of Nd/Al2O3 catalysts calcined at 400?°C followed by optimization with respect to calcination temperatures, based ratios loading and various Ru loading. The Ru/Mn/Nd (5:20:75)/Al2O3 calcined at 1000?°C was the potential catalyst, attaining a complete CO2 conversion and forming 40% of CH4 at 400?°C reaction temperature. XRD results revealed an amorphous phase with the occurrence of active species of RuO2, MnO2, and Nd2O3, and the mass ratio of Mn was the highest among other active species as confirmed by EDX. The ESR resulted in the paramagnetic of Nd3+ at the g value of 2.348. Meanwhile nitrogen adsorption (NA) analysis showed the Type IV isotherm which exhibited the mesoporous structure with H3 hysteresis of slit shape pores. 相似文献
11.
SiO和AlO负载的Ni基催化剂在甲烷干重整中的催化性能差异 《燃料化学学报》2019,47(2):199-208
CH4与CO2干重整反应对于环境保护和天然气资源的合理利用具有重要意义。SiO2和Al2O3是适用于甲烷干重整反应的两种典型的催化剂载体。为了阐明这两种载体对催化剂性能的影响,本研究采用等体积浸渍法制备了Ni/Al2O3和Ni/SiO2催化剂,并利用BET、TEM、H2-TPR、XRD、TG和Raman等技术对还原和反应后的催化剂进行了表征。结果表明,由于载体的性质不同,Ni基催化剂在甲烷干重整中的催化性能也不同。Ni/SiO2催化剂的初始活性较高,但由于其金属-载体相互作用较弱,催化稳定性较差,在800℃下反应15h其催化活性急剧下降;较弱的金属-载体相互作用使得Ni/SiO2催化剂上的Ni颗粒较大,有利于积炭前驱物种的生成,导致催化剂快速失活。而对于Ni/Al2O3催化剂,金属-载体相互作用较强,Ni颗粒较小,但由于Ni与Al2O3生成了NiAlxOy物种,有效活性位减少,其催化活性相对较低,但催化稳定性较好,干重整反应进行50h其活性保持稳定;Ni与Al2O3之间较强的相互作用有利于形成小且稳定的Ni粒子,能减少积炭,因而具有优异的催化稳定性。 相似文献
12.
The Er3+-doped Al2O3 nanopowders have been prepared by the sol-gel method, using the aluminium isopropoxide [Al(OC3H7)3]-derived γ-AlOOH sols with addition of the erbium nitrate [Er(NO3)3·5H2O]. The five phases of γ-(Al,Er)2O3, θ-(Al,Er)2O3, α-(Al,Er)2O3, ErAlO3, and Al10Er6O24 were detected with the 0–20 mol% Er3+-doped Al2O3 nanopowders at the different sintering temperature of 600–1200°C. The average grain size was increased from about 5 to 62 nm
for phase transformation of undoped γ-Al2O3→α-Al2O3 at the sintering temperature from 600 to 1200°C. At the same sintering temperature, average grain size was decreased with
increase of the Er3+ doping concentration. Infrared absorption spectra of γ-Al2O3 and θ-Al2O3 nanopowders showed the two broad bands of 830–870 and 550–600 cm−1, the three broad bands of 830–870, 750–760, and 550–600 cm−1, respectively. The infrared absorption spectra for the α-Al2O3 nanopowder showed three characteristic bands, 640, 602, and 453 cm−1. The two characteristic bands of 669 and 418 cm−1 for Er2O3 clusters were observed for the Er3+-doped Al2O3 nanopowders when Er3+ doping concentration was increased up to 2 mol%. The 796, 788, 725, 692, 688, 669, 586, 509, 459, and 418 cm−1 are the characteristic bands of Al10Er6O24 phase. 相似文献
13.
The effects of doping with CeO2 and calcination temperature on the physicochemical properties of the NiO/Al2O3 system have been investigated using DTA, XRD, nitrogen adsorption measurements at −196°C and decomposition of H2O2 at 30–50°C. The pure and variously doped solids were subjected to heat treatment at 300, 400, 700, 900 and 1000°C. The results
revealed that the specific surface areas increased with increasing calcination temperature from 300 to 400°C and with doping
of the system with CeO2. The pure and variously doped solids calcined at 300 and 400°C consisted of poorly crystalline NiO dispersed on γ-Al2O3. Heating at 700°C resulted in formation of well crystalline NiO and γ-Al2O3 phases beside CeO2 for the doped solids. Crystalline NiAl2O4 phase was formed starting from 900°C. The degree of crystallinity of NiAl2O4 increased with increasing the calcination temperature from 900 to 1000°C. An opposite effect was observed upon doping with
CeO2. The NiO/Al2O3 system calcined at 300 and 400°C has catalytic activity higher than individual NiO obtained at the same calcination temperatures.
The catalytic activity of NiO/Al2O3 system increased, progressively, with increasing the amount of CeO2 dopant and decreased with increasing the calcination temperature. 相似文献
14.
The performance of a new lab-made bifunctional material Ni/Al2O3/KNaTiO3 for producing high purity H2 via sorption-enhanced steam methane reforming (SESMR) was investigated. A series of bifunctional materials with 10 wt% Ni loading but different wt% ratios of KNaTiO3 and Al2O3 was prepared by wetness impregnation method. All the materials were calcined at 700 °C for 3 hours and screened for their catalytic activity in a continuous flow fixed-bed reactor. The material containing 50 wt% each of KNaTiO3 and Al2O3 (designated as HM) was found to be the best choice. The optimum process parameters for the production of high purity H2 were determined: temperature = 700 °C, steam to carbon (S/C) molar ratio = 6 and gas-hourly space velocity (GHSV) = 2000 cm3 g-1 h-1. The values of CH4 conversion, H2 yield and H2 purity were 87, 87 and 90%, respectively, at the optimum reaction conditions. The adsorption capacity of HM was found to be 14.7 wt%. With a breakthrough time of 10 min, the material was stable for 8 adsorption-desorption cycles. The regeneration of HM was achieved with N2 gas at the same reaction temperature. Overall, the activity of this material for SESMR was very promising. 相似文献
15.
Novel γ-Al2O3 supported nickel (Ni/Al2O3) catalyst was developed as a functional layer for Ni–ScSZ cermet anode operating on methane fuel. Catalytic tests demonstrated Ni/Al2O3 had high and comparable activity to Ru–CeO2 and much higher activity than the Ni–ScSZ cermet anode for partial oxidation, steam and CO2 reforming of methane to syngas between 750 and 850 °C. By adopting Ni/Al2O3 as a catalyst layer, the fuel cell demonstrated a peak power density of 382 mW cm?2 at 850 °C, more than two times that without the catalyst layer. The Ni/Al2O3 also functioned as a diffusion barrier layer to reduce the methane concentration within the anode; consequently, the operation stability was also greatly improved without coke deposition. 相似文献
16.
Hydrogenation of furfurylidene acetone has been carried out using Ni/γ−Al2O3 and Cu/γ−Al2O3 catalyst in the presence of isopropanol in autoclave batch reactor. The hydrogenation using Cu/γ−Al2O3 at 120oC for 6 h gives main formation of 1,5-bis-(furan-2-yl)-pentan-3-one. Reaction at higher temperature at 140oC for 8 h using Ni/γ−Al2O3 leads to 1,5-bis-(furan-2-yl)-penta-1-en-3-one. The different selectivity of both catalysts is explained by physical properties including the surface area and distribution of metal loading. 相似文献
17.
《Journal of Energy Chemistry》2014,23(2):235-243
A series of novel Ni/CeO2-Al2O3composite catalysts were synthesized by one-step citric acid complex method. The as-synthesized catalysts were characterized by N2physical adsorption/desorption, X-ray diffraction(XRD), Fourier transform infrared(FT-IR) spectroscopy, hydrogen temperature-programmed reduction(H2-TPR), X-ray photoelectron spectroscopy(XPS) and thermogravimetry analysis(TGA). The effects of nickel content, calcination and reaction temperatures, gas hourly space velocity(GHSV) and inert gas dilution of N2on their performance of catalytic partial oxidation of methane(CPOM) were investigated. Catalytic activity test results show that the highest methane conversion(85%), the best selectivities to carbon monoxide(87%) and to hydrogen(95%), the excellent stability and perfect H2/CO ratio(2.0) can be obtained over Ni/CeO2-Al2O3with 8 wt% Ni content calcined at 700 ℃ under the reaction condition of 750 ℃, CH4/O2ratio of 2 : 1 and gas hourly space velocity of 12000 mL h-1 g-1. Characterization results show that the good catalytic performance of this composite catalyst can be contributed to its large specific surface area(~108 m2 g-1), small crystallite size, easy reducibility and low coking rate. 相似文献
18.
Fe-Ag/AlO催化丙烯还原NO的实验研究 《燃料化学学报》2017,45(11):1365-1375
以蜂窝状陶瓷为载体,采用溶胶凝胶法和浸渍法制备了不同Fe/Ag负载量的Fe-Ag/Al_2O_3催化剂。以C_3H_6为还原剂,在模拟烟气条件下和200-700℃范围内,程序控温的陶瓷管流动反应器上进行了催化还原NO的性能评估。结果表明,7.2Fe/1.9Ag/20Al_2O_3/CM在500和550℃时催化C_3H_6还原NO的脱硝效率分别超过90%和达到100%。铁离子能有效地提高Ag/20Al_2O_3/CM催化剂抵抗烟气中的SO_2和H_2O的能力。结果表明,当烟气中含有体积分数为0.02%的SO2和8%的H_2O时,在500℃时7.2Fe/1.9Ag/20Al_2O_3/CM催化C_3H_6还原NO的脱硝效率不受影响,在6 h的连续实验中保持90%的脱硝效率而没有下降。而未经铁离子修饰的2Ag/20Al_2O_3/CM的催化活性则受烟气中的SO2和H_2O影响很大,0.02%的SO2和8%的H_2O分别使2Ag/20Al_2O_3/CM在500℃时催化C_3H_6还原NO的脱硝效率迅速从70%分别下降至46%和25%。XRD和SEM表征结果表明,经铁离子修饰后的7.2Fe/1.9Ag/20Al_2O_3/CM催化剂中,形成了AgFeO_2以及Fe~(3+),催化剂表面变得疏松多孔,形成以Fe_3O_4为主的针状和片状晶体。H_2-TPR结果表明,7.2Fe/1.9Ag/20Al_2O_3/CM比Ag/20Al_2O_3/CM在更宽的温度范围内具有更好的还原特性。吡啶吸附红外光谱(Py-FTIR)实验结果显示,Fe增加了催化剂表面的Lewis酸性位。 相似文献
19.
Huimei Duan Rui You Shutao Xu Zhaorui Li Kun Qian Tian Cao Weixin Huang Xinhe Bao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12171-12176
Supported Pd catalysts are active in catalyzing the highly exothermic methane combustion reaction but tend to be deactivated owing to local hyperthermal environments. Herein we report an effective approach to stabilize Pd/SiO2 catalysts with porous Al2O3 overlayers coated by atomic layer deposition (ALD). 27Al magic angle spinning NMR analysis showed that Al2O3 overlayers on Pd particles coated by the ALD method are rich in pentacoordinated Al3+ sites capable of strongly interacting with adjacent surface PdOx phases on supported Pd particles. Consequently, Al2O3‐decorated Pd/SiO2 catalysts exhibit active and stable PdOx and Pd–PdOx structures to efficiently catalyze methane combustion between 200 and 850 °C. These results reveal the unique structural characteristics of Al2O3 overlayers on metal surfaces coated by the ALD method and provide a practical strategy to explore stable and efficient supported Pd catalysts for methane combustion. 相似文献
20.
《Journal of Energy Chemistry》2014,23(4):461-467
Palladium catalysts are supported on TiO2, ZrO2, Al2O3, Zr0.5Al0.5O1.75 and TiO2-Zr0.5Al0.5O1.75 prepared by co-precipitation method, respectively. Catalytic activities for methane and CO oxidation are evaluated in a gas mixture that simulated the exhaust from lean-burn natural gas vehicles (NGVs). Pd/TiO2-Zr0.5Al0.5O1.75 performs the best catalytic activity among the tested five catalysts. For CH4, the light-off temperature (T50) is 254 °C, and the complete conversion temperature (T90) is 280 °C; for CO, T50 is 84 °C, and T90 was 96 °C. Various techniques, including N2 adsorption-desorption, X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) are employed to characterize the effect of supports on the physicochemical properties of prepared catalysts. N2 adsorption-desorption and SEM show that TiO2-Zr0.5Al0.5O1.75 expresses uniform nano-particles and large meso-pore diameters of 26 nm. H2-TPR and XRD indicate that PdO is well dispersed on the supports and strongly interacted with each other. The results of XPS show that the electron density around PdO and the proportion of active oxygen on TiO2-Zr0.5Al0.5O1.75 are maxima among the five supports. 相似文献